code: def train(
      fabric,
      model,
      optimizer,
      train_dataloader,
      val_dataloader,
      max_epochs=20,
  ):
      for epoch in range(max_epochs):
          train_epoch(fabric, model, optimizer, train_dataloader, epoch)
          val_loss = validate(fabric, model, val_dataloader)
          fabric.print(f"val loss {val_loss.item():.4f}")
  
file_path: pytorch-lightning/examples/fabric/language_model/train.py
imports: import lightning
  import torch
  import torch.nn.functional
  from lightning.pytorch.demos import Transformer, WikiText2
  from torch.utils.data import DataLoader, random_split
label_desc: Use image node_id 2 for calling a global function with example usage: train(fabric, model, optimizer, train_dataloader, val_dataloader, max_epochs) without return types